Many thiazolidine compounds are used as important architectures of drugs due to biological activities thereof. For example, Taiwan patent No. 1323659 provides a novel thiazolidin-4-one derivative, which can be used as an immunosuppressive agent that achieves the aim of an immunosuppressive effect effectively and durably by reducing the number of T lymphocytes and B lymphocytes cycles and infiltration.
With respect to synthesizing method of thiazolidine compounds, Rozwadowska et al. published a method in 2001, reacting an isoquinoline (formula 1) with thioglycolic acid through cycloaddition reaction to synthesize a thiazolidinedione (formula 2), and meanwhile they tried to obtain a thiazolidine derivative (formula 3) by reacting the isoquinoline (formula 1) with thiirane. However, the time of synthesis reaction was as long as 30 hours, and the productivity is also not very ideal (32%). (Rozwadowska, M. D.; Sulima, A. Tetrahedron 2001, 57, 3499-3506)

In 2003, Gu, X. et al. published a method that reacts an amino acid with an aldehyde compound (formula 4) through cycloaddition reaction to synthesize a thiazolidine derivative (formula 5), but the required reaction time is 4 days while the productivity is only 55%. Thus there can still improve the way of synthesizing route. (Gu, X.; Cowell, S.; Ying, J.; Tang, X.; Hruby, V. J. Tetrahedron Lett. 2003, 44, 5863-5866)

Additionally, as published in 2001, Osante et al. studied a cyclization method of a heterocyclic molecule, in which the author obtained a compound (formula 7) through a cycloaddition reaction after using the compound thiazolidinedione (formula 6) as the starting material and deprotonating the benzene ring under a strong alkaline condition. Although the synthesis conditions disclosed in this literature improved the reaction time greatly, but the reaction had to be conducted under the strong alkaline condition and the preparation steps of the starting material were also very complicated, and in addition the productivity was also not very high as only 49%. (Osante, I.; Collado, M. I.; Lete, E.; Sotomayor, N. Eu. J. Org. Chem. 2001, 1267-1277)

It can be seen from the aforementioned synthesis history that, for the synthesis of thiazolidine compounds, the development of such type of compound is often limited due to reasons such as the reaction is time-consuming, the demand of using a strong alkali or acid in the reaction condition, or the difficulty of obtaining the starting material of the reaction. In view of this, it is an urgent need to develop a synthesis method which can meet the industry demands, so as to solve the choke points encountered during current development of thiazolidine compounds.